If I understand OP - is looking for the long bevels to be equal distance (easy per @NeilCooke suggestion). Then the end bevels sb 'flatter' using two distance bevel works EXCEPT - getting the corner triangles as OP shows is not trivial. Here is document . I made this by doing corner bevels after long bevels and then the end edge bevels - then went back to adjust the corner 'Distance 1' by trial and error to 5 places (could have measured it with sketch...) and it is not perfect. I would be tempted to just create a loft surface to trim the corners...

I think this is it. After i posted the question, i also tried with planes on each corner but it was complicated. Also, when i wanted to change the distance between front and the rest of object, the "triangles" in the corners didn't follow the change. Thank you. I see you have used some mirroring and split tricks, i'll try to understand this.

If I understand OP - is looking for the long bevels to be equal distance (easy per @NeilCooke suggestion). Then the end bevels sb 'flatter' using two distance bevel works EXCEPT - getting the corner triangles as OP shows is not trivial. Here is document . I made this by doing corner bevels after long bevels and then the end edge bevels - then went back to adjust the corner 'Distance 1' by trial and error to 5 places (could have measured it with sketch...) and it is not perfect. I would be tempted to just create a loft surface to trim the corners...